The effect of adrenoceptor blockade on the release of gastric inhibitory polypeptide after intraduodenal glucose in humans.

An intravenous infusion of NaCl, NaCl + phentolamine (alpha-adrenoceptor antagonist), or NaCl + propranolol (beta-adrenoceptor antagonist) was given in three series of experiments. After intraduodenal infusion of glucose (82 ml 1.51 M, pH 6.5) the GIP concentration in plasma increased from 42.3 (23.1-62.2) to 225 (107-460) pM during intravenous NaCl, from 35.6 (17.3-38.9) to 251 (127-387) pM during phentolamine, and from 32.5 (5.5-63.4) to 172 (103-405) pM during propranolol administration. The blood glucose response was not different in the three experiments. It is concluded that the non-selective beta-adrenoceptor antagonist propranolol inhibits the release of GIP after intraduodenal administration of glucose.